But alas, no Beatles. And back then, the possibility of a comeback utterly dominated the news cycle. McCartney, brought in by then-U.N. Secretary General Kurt Waldheim to spearhead the huge benefit, tried to refocus everyone.

"The Beatles are over and finished with," McCartney reiterated to The New York Times a few weeks earlier. "None of us is even interested in doing it. There's lots of reasons. Imagine if we came back and did a big show that wasn't good. What a drag."

The blame for this distraction, ironically enough, pointed to Waldheim. In an effort to drum up interest in the Kampuchea concerts, he'd stirred up a second wave of Beatlemania. Waldheim initially approached McCartney, hoping his current band Wings would participate. But he also discussed a performance with George Harrison, and then the gossip wheel began whirring.

McCartney agreed to come on board because he wanted to do something for Cambodia, where the Pol Pot-led Khmer Rouge regime had killed millions of people in the late '70s, creating a refugee crisis. McCartney initially heard about this crisis on a BBC TV program, which sparked outrage and then a desire to help.

"Like most people, I saw the film of the starving kids," McCartney told Rolling Stone in 1980. "It was a soul-searching bit of film."

Watch Queen Perform at 'Concerts for Kampuchea'

Harrison ended up backing out, while McCartney helped assemble a once-in-a-lifetime lineup that bridged generations while training a more intense spotlight on the horrors going on in Cambodia.

"Between 1975 and 1979, Kampuchea lost up to half of its population through war, famine and disease. Waldheim called it 'a national tragedy, the proportions of which may have no parallel in history,'" Atlantic Records executive Bob Kaus said in the liner notes for the subsequent two-record set commemorating the Concerts for the People of Kampuchea. “[Their plight] stirred musicians to lend their talents, time and energy to do what they [could] to help relieve the massive suffering. The call for help was issued [for] the greatest gathering of British rock talent ever assembled for a single event."

The concerts opened with a 28-song set by Queen, who were the only performers on Dec. 26. The Clash, who had just released their career-making London Calling two weeks before, closed out Day 2 after performances by Ian Dury and the Blockheads and Matumbi. Dec. 28 showcased the Pretenders (who hadn't yet released their smash debut), Specials and the Who. The final night featured Costello and the Attractions, Rockpile (who were joined by Plant for "Little Sister") and then Wings on Dec. 29.

McCartney then welcomed an incredible slate of artists onstage for a show-closing performance from his so-called Rockestra. The lineup included Plant, John Bonham and John Paul Jones from Led Zeppelin; Pete Townshend and Kenny Jones of the Who; Ronnie Lane from Faces; Gary Brooker from Procol Harum; Dave Edmunds from Rockpile; James Honeyman-Scott of the Pretenders; and Bruce Thomas from the Attractions.

They played the "Rockestra Theme," a Grammy-winning instrumental from Wings' recent Back to the Egg album, along with covers of Little Richard's "Lucille" and the Beatles' "Let It Be." The finale's improvisational nature ended up providing an unlikely showcase for Wings member Laurence Juber.

"We had all these great guitarists onstage, and when it came time for the guitar solo in 'Let It Be,' I didn't think anyone else was going to step in and play the guitar solo,” Juber told the Times Record in 2015. "Wings had been doing that song on tour, so I just stepped out in front of all my heroes and played the solo that night."

Despite all of that star power, the Beatles' long shadow remained. Speculation about a possible reunion, rather than fading, had only intensified as showtime approached.

Watch Rockestra Perform at 'Concerts for Kampuchea'

"Some woman [Pauline McLeod] wrote in a newspaper [the Daily Mirror] that she had evidence it was definitely on – which is a load of bull, because it wasn't," McCartney told Rolling Stone. "That was blown up in the papers, and the papers were saying, 'Can you tell us who your guests are, please?' I just said no."

Not long before Wings were set to go onstage, ABC reportedly sent word that the network would pay an astounding $2,000 for as little as two minutes of film of a Beatles reunion. That brought so many ticket scalpers, autograph seekers and general hangers-on to the venue that Wings were unable to escape from the Odeon after their soundcheck.

Bored by hours of waiting around, Wings did a "good deal of drinking," according to Howard Sounes' Fab: An Intimate Life of Paul McCartney. "It was a pretty messed-up deal," McCartney's drummer Steve Holley noted. "I don't think the performance was particularly good."

At one point, buzz moving through the crowd indicated that John Lennon had arrived on site. He hadn't. Instead, the Concerts for the People of Kampuchea marked two significant – though more typically overlooked – moments.

Bonham never appeared onstage in England again. "After the show, we returned to Blakes Hotel, along with Jonesy, who was also staying there," Bonham's brother Mick said in his book Bonham by Bonham "Upon finding a small bar with a piano, we finished off the evening singing some old classics with great backing by John Paul Jones." Bonham died the following September.

Wings never played another show. The band was in the midst of a world tour that was set to land in Japan next. Then McCartney got busted for pot on Jan. 16, 1980, in Tokyo, and ended up spending nine days in jail. Wings' entire tour was scrapped because of subsequent visa problems.

They got back together twice in 1980, in July and October, for work on a possible studio follow-up to Back to the Egg, before officially breaking up not long after the Concerts for the People of Kampuchea album arrived in 1981. The material from Wings' final sessions with McCartney ended up scattered throughout 1982's Tug of War and 1983's Pipes of Peace.